A complement (after years) : If you are using a fake certificate like snakeoil with virtualhosts (sure at development time!) you have to use 'verify_peer_name'=>false like :

'ssl' => [
    //'verify_peer' => false, <- not needed with "allow_self_signed=true"
    'verify_peer_name' => false, // <- this one is mandatory
    'allow_self_signed' => true
],

Cheers.